The present inventive concept relates to a global positioning system (GPS). More particularly, the present inventive concept relates to a GPS receiver and positioning method implemented by the GPS receiver.
Generally, GPS was developed to measure locations of objects, typically in latitude, longitude and/or altitude. For example, GPS services enable a user to determine his or her location by receiving GPS signals from a constellation of GPS satellites, measuring information for the current location, and providing the measured information to the user.
In addition, GPS services are utilized for navigation purposes using additional data, such as map information, traffic information, and the like. For example, when a user selects a destination, navigation information, such as traffic or direction information from the current location to the selected destination, is provided to the user using previously stored map information. Further, GPS services have been applied to various fields, such as military maneuvers, aeronautical operations, air traffic control, and the like. In addition to location information, it is possible to acquire time references from GPS satellites.
GPS services require orbiting GPS satellites for broadcasting GPS signals, and a GPS receiver for calculating location information in response to the received GPS signals. Currently, GPS services depend on a GPS constellation, which includes twenty-four GPS satellites orbiting Earth in different orbits (in particular, twenty-seven GPS satellites orbit the Earth, three of which are supplemental satellites). In order to determine its location, the GPS receiver must acquire GPS signals from at least four of the GPS satellites. That is, the GPS receiver must lock onto signals from four or more GPS satellites.
However, when there is jamming or interference due to other radio waves or physical obstructions, such as buildings, forests, and the like, the GPS receiver may not be able to lock onto four or more GPS satellites. In this case, the GPS receiver is unable to accurately determine its location using GPS services.